Servomotor control system for airplanes



Nov. 26, 1940. vOIGT 2,222,886

- SERVOMOTOR CONTROL SYSTEM FOR AIRPLANES Filed Jan. 16, 1937 trolsurfaces.

Patented Nov. 26, 1940 w UNITED STATES PATENT A OFFICE SERVOMOTOR-CONTROL SYSTEM FOR AIRPLANES Waldemar Voigt, Haunstetten, near Augsburg,Germany, assignor to Siemens Apparate und Maschinen (Gesellschaft mitbeschriinkter Haftung), Berlin, Germany, a corporation of GermanyApplication January 16, 1937, Serial No. 120,888 In Germany January 16,1936 5 Claims. (01. 244-48) This invention relates to airplanes and moreReferring more particularly to the drawings, particularly to theoperation of the control surin Fig. 1 a control lever 11., pivoted at afixed faces wherein an auxiliary source of power is point on theairplane fuselage, carries at its employed .to assist the pilot inmoving the conlower end, pivotally attached thereto, a rod consisting oftwo sections b and c. The outer end One of the objects of the presentinvention is of section 0 is pivotally connected to the'operatto providea servomotor interconnected with the .ing lever d of the airplaneelevator 10. Between manually controlled lever to assist the pilot inthe control rod sections b and c is arranged the effectively moving theelements of an airplane valve means am such a manner that the casingwhile in flight. of the valve is pivotally connected to the inner In thepreferred embodiment it is a further end of the rod section c while theinner end of object of this invention to interconnect the manrodsection 1) passes through a guide 1 into the ually controlled lever withthe servomotoi' in such valve casing where it is connected to a movablea manner as to effect a reaction on the former member 2, shown in detailin Fig. 2. Two conwhen the latter is operated. duits g and h leadfrom'each end of the valve It is a further object to provide an adjusteto" each end of the fluid operated servomotor able connection betweenthe manually controlled cylinder 1' which is also pivoted at a fixedpoint lever and the servomotor by which the amount on the airplanefuselage. Cylinder i contains a of reaction on the former from thelatter may sliding piston 7 which is pivotally attached, at a be varied.suitable point through the piston rod k,'to the It frequently happensthat dangerous stresses control rod section 0. Fluid under pressure isand strains are built up in the airplane strucsupplied to the valve ethrough a conduit 1 from ture as for instance when recovering rapidly apump m driven by the main power plant of the from a nose dive.Accordingly, it is a further airpla a d s ar conduit 0 leads from theobject of this invention to provide a mechanism valve e back to thesuction side of the pump. I

which will automatically and temporarily take If desired, a Pressure aor 1t may be inover the operation of the control surfaces ofterconnected with the conduit 1. the plane in the event that suchstresses and n F th V v 8 f Fl 1 and 3 iS- Shown strains are developedto an excessive degree durin Cress-Section and consists of a casing llling flight. ing on the inside small recessed ports 4 and 5.

These and other objects of the invention will Att hed t h center f "t ason pp become apparent from inspection of th followsite sides thereof,are conduits l and 0 which ing specification when read with reference torepresent pe e y the fl et nd i the accompanying drawings wherein isillustrateharge- At h e d' of the casing,,oonduits 9 ed thepreferredembodiment of the invention. nd h lead to opposite ends of theservomotor It is to be expressly understood, however, that Cylinder 11The piston Valve 2 is 'recessed as the drawings are for the purpose ofillustration wn a 211 for cooperation with the p s 4 only and are notdesigned as a definition of the o 5 d is operated y eans of the controllimits of the invention, reference being had to red Section The casingla is p v t y 0011- the appended claims for that purpose. nected to theinner end of control rod section 40 In the drawings; 0. Adjustable stopscrews 8 and I, carried by Fig. 1 shows diagrammatically one form of thecasing, serve to limit the piston travel. auxiliary w r t l for tapplication of The auxiliary control, diagrammatically illusfluidpressure for operating the elevator of an trated in Operates in thefollowing manairplane; hell Fig 2 shows, i t t preferred form When thecontrol lever a is moved in the diof the control valve diagrammaticallyillustrated motion indicated by the arrow, a force s transat e in Fig.1; I mitted through the argi/section b to move the Fig. 3 showsdiagrammatically the preferred V v 2 t h l ainst the adjustable stopform of the auxiliary power contro1; screw 6. This interconnectsconduits Z and g Fig. 4 shows, in section, the control valve diathroughthe recessed ports 2a and 4, thereby grammatically illustrated at e" inFig. 3, and subjecting the right hand side of piston 1' to Fig. 5 shows,in section, the adjustable confluid pressure. The other side of thepiston is nection diagrammatically illustrated at q in Fig. connected tothe discharge through conduits h 3. and 0. As the piston 9' moves to theleft under the action of fluid pressure, it draws the control rodsection 6 with it by means of the piston rod is, thereby moving theelevator 11 in an upwardly direction. As the control rod section 0 movesto the left, the valve casing I0, being pivotally connected thereto, isalso moved to the left and if the control rod section 'b is heldstationary, valve 2 will thereby lap ports I and o.

In the event of power failure, the manual effort applied to the lever ain the direction of the arrow, will move the elevator p in an upwarddirection since a linkage connection is formed by the lever a, controlrod section b, valve 2, stop screw 6, casing l0 and control rod sectiona.

The area of piston a and the pressure of the fluid may be varied toexert any desired force, such as for example, a force less than thatrequired to actuate the control surface p so that it will functionmerely as an assistor.

In Fig. 3 is shown, diagrammatically, the preferred embodiment of thisinvention and consists of parts similar to that of Fig. 1. The controlrod a carries, just below its fixed pivot, an externally threaded,rotatable sleeve q which cooperates with an internally threadednon-rotatable ring l2, shown in detail in Fig. 5. This ring is connectedto the servomotor cylinder casing through the rod T which is pivoted ateach end.

A control valve e" is interposed in the inlet and discharge conduits Zand o and is interconnected with the conduits g and h by means ofconduits g and h" respectively. This valve serves to control the fluidpassing through the valve e in accordance with certain conditionsreferred to hereinafter.

In Fig. 4, the control valve e" of Fig. 3, is shown in cross-section andconsists of a casing I0" firmly afiixed in a vertical position to thefuselage of the airplane. The piston valve 2" is provided on each sidewith annular recesses l4 and I6 formed between the smaller pistons l 8and 20 which are connected to the main piston 2" through stems 22 and24. Adjustable stops 6" and 1" are provided in each end of the casing.Normally the inlet conduit 1 is continuous through recess l4 while thedischarge conduit 0 is continuous through recess l6. Conduits g" and h"interconnect with conduits g and h of the control valve e and arenormally covered by the pistons 2 and I8 respectively. The piston valveis pressed against the upper stop by means of a spring 9.

The connections between the threaded sleeve q and the servomotor casingare preferably formed in such a manner that the first movement of thelever a actuates the valve e to energize the servomotor.

The force exerted by the servomotor 1' through the pivoted rod r andring l2 on the sleeve q is less than the total force required to actuatethe control surface 17 and therefore only assists the operator in movingthe rod a clockwise. This assisting force may be increased or decreasedas the operator desires by rotating the sleeve q and thereby adjustingthe ring I2.

Normally the operation of Fig. 19a is similar to that of Fig. 1.Recesses l4 and IS in valve e" permit the flow of fluid to and from thevalve 6 and servomotor i without interruption. When, however, theairplane is righted after a nose dive, the centrifugal accelerationwhich occurs, owing to the upward curvature of the flight path, willmanifest itself in increased weight of all the various parts. Thisweight, if unduly increased, may endanger the airplane structure.

The tension of spring 9 is so adjusted that excess centrifugalacceleration will force the valve piston 2" downwards. In this newposition, the inlet conduit l and the discharge conduit 0 will be closedoff by the pistons 2" and 20. By closing off the normal inlet anddischarge conduits, the conduits g" and h" will be uncovered and theflow of fluid will then be through the conduit 1, recess I 4, conduit71." into the left-hand side of servomotor 2'; The discharge on theright-hand side of the cylinder will be through conduits g, g, recess l6and conduit 0.. This .will cause the piston a to move to the right andthrough the piston rod is and control rod section 0 the elevator 1: willbe moved in a clockwise direction, thereby reducing the upward path ofthe airplane. When this upward path has been modified so thatcentrifugal action no longer affects the piston valve, the spring 9 willpush it up to its normal position thereby reestablishing the fiow offluid as in normal flight.

This auxiliary valve e may be designed so that it can be made entirelyineffective in extreme emergency cases where the altitude of theairplane is insuflicient to permit a safe path of acceleration.

It is obvious that the invention disclosed includes within its scope theactuation of other elements or objects aside from those mentionedherein, which require the use of auxiliary power for their operation.

While one illustrated embodiment of the invention has been described indetail, it is not my intention to limit its scope to that embodiment orotherwise than by the terms of the appended claims.

What is claimed is:

1. In an-airplane having a controlled member, a controlling leverconnected thereto for directly actuating the same, means including aservomotor having a connection. with said controlled member for movingthe latter by power, said servomotor having relatively movable elements,one element thereof connected to the controlled member for moving thelatter in either of two directions, means connecting the other elementto said controlling lever, an adjustable coupling forming a part of saidconnecting means, control mechanism for governing the energization ofsaid servomotor, said mechanism including a movable device connectedwith said controlling lever whereby movement of the latter in oppositedirections serves to energize said servomotor in opposite directions,and means responsive to centrifugalforce developed in the airplanetravelling in a curved path during a sudden recovery from a dive forchanging the energization of said servomotor. V

2. In anairplane having a controlled element, a controlling member,means including a power actuator having a connection with saidcontrolled element for moving the latter by power, control mechanism forgoverning the energization of said power actuator, said mechanismcomprising a pair of valves separate from each other, the first of whichis cooperatively associated with the said controlling member forgoverning the energize.- tion of said power actuator, the second ofwhich is cooperatively associated with said first valve and with saidpower actuator for energizing the power actuator independently of saidfirst valve when the latter is in one position.

3. In an airplane having a controlled member,

a controlling member, means including a power actuatorhaving aconnection with said controlled member for moving the latter by power,control mechanism for governing the energization of said power actuator,said mechanism including a movable device connected with saidcontrolling member whereby movement of the latter in opposite directionsserves to energize said actuator in opposite directions, additionalmeans separate from said mechanism cooperatively associated with saidmovable device and with said power actuator, said means including amember subjected to the action of centrifugal force developed in theairplane travelling in a curved path by a sudden recovery from a divefor changing the energization of said power actuator when said movabledevice is in one position.

4. In an airplane having a controlled member,

'a controlling lever connected thereto for directly actuating the same,means including a servomotor having a connection with said controlledmember for moving the latter by power, said servomotor having relativelymovable elements, one element thereof connected to the controlled memberfor moving the latter, the other element thereof connected to saidcontrolling lever, control mechanism for governing the energization ofsaid servomotor, said mechanism comprising a pair of valves, the firstof which is cooperatively associated with the said controlling lever forgoverning the energization of said servomotor, the second of which iscooperatively associated with said first valve and with said servomotorfor energizing the servomotor independently of said first valve when thelatter is in one position.

5. In an airplane having a controlled element,

.a controlling lever connected thereto for directly actuating the same,means including a servomotor having a connection with said controlledelement for moving the latter by power, control mechanism for governingthe energization of said servomotor, said mechanism including a controlvalve connected with said controlling lever whereby movement of thelatter in opposite directions serves to energize said servomotor inopposite directions, a pilot valve cooperatively associated with saidcontrol valve and with said servomotor, said pilot valve comprising aresiliently supported piston normally controlling the supply of pressurefluid to the control valve, said piston being responsive to the actionof centrifugal force developed by the airplane travelling in a curvedpath in response to a sudden recovery from a dive for closing the flowof pressure fluid to said control valve and opening the flow of pressurefluid to said servomotor whereby the latter is energized independentlyof the control valve, when the control valve is in one position.

WALDEMAR VOIGT.

